False negatives are spam messages that SpamSieve examined but didn’t think were spam. This option causes SpamSieve to save such messages for later analysis. Clicking the Show button opens the folder containing the saved messages. You can e-mail this folder, or selected files from it, to spamsieve-fn@c-command.com. By looking at the messages that SpamSieve missed, I can improve its algorithms to catch such messages in the future. Note that enabling this option will slow down SpamSieve’s processing.